1. Field of the Invention
The present invention relates to an Active Matrix Organic Light Emitting Diode (AMOLED) display and a method of controlling a display thereof. More particularly, the present invention relates to an AMOLED display and a method of controlling a display thereof that use a cholesteric Liquid Crystal Display (LCD) that can operate in a low power mode or a high picture quality mode.
2. Description of the Related Art
Nowadays, as a display used for a mobile terminal or an e-paper, an AMOLED display or a Liquid Crystal Display (LCD) are widely available. More particularly, an LCD is classified as a transmissive LCD, a reflective LCD, or a transflective LCD, according to a display method.
Because the transmissive LCD uses a backlight, a panel, and a line polarizing plate, the transmissive LCD has a low efficiency backlight, consumes a relatively large amount of current, and has low outdoor visibility. The AMOLED display that displays a screen without using external light has a high optical characteristic, but also consumes a relatively large amount of power.
The reflective LCD uses external light as a light source using a reflector, a panel, and a circular polarization plate, and has a reflexibility of less than 20%. Thus, the reflective LCD cannot display a screen at a location having a low indoor visibility and having no external light. The reflective LCD uses a cholesteric LCD, and a related art cholesteric LCD is described with reference to FIG. 1.
FIG. 1 is a perspective view illustrating a cholesteric LCD of the related art.
Referring to FIG. 1, a cholesteric LCD 10 includes an absorption layer 11, a first cholesteric liquid crystal color layer 12 in which a first transparent electrode film 15 is attached to an upper surface thereof, a second cholesteric liquid crystal color layer 13 in which a second transparent electrode film 16 is attached to an upper surface thereof, and a third cholesteric liquid crystal color layer 14 in which a third transparent electrode film 17 is attached to an upper surface thereof. The absorption layer 11, the first cholesteric liquid crystal color layer 12, the second cholesteric liquid crystal color layer 13, and the third cholesteric liquid crystal color layer are sequentially stacked. In the cholesteric LCD 10, power is required only when a state of one or more of the cholesteric liquid crystal color layers 12, 13, and 14 changes, and thus the cholesteric LCD 10 has bistability, very low power consumption, a low optical characteristic, and a slow response speed.
The transflective LCD has a portion operating as a reflective LCD and other portions operating as a transmissive LCD by disposing a reflector at a part of a pixel, and has a structure entailing a little lower transmitting characteristic and higher outdoor visibility than that of the transmissive LCD. However, because of the reflector, the transflective LCD has a reduced aperture ratio, resulting in low luminance, and a reduced color reproduction ratio. Further, in order to obtain a desired color reproduction ratio, reflexibility is limited to about 2% to 5%, and therefore it is difficult to apply a high specification of display and to apply AMOLED technology. Further, due to the expansion of the e-book market, a further limitation has become increasingly important in reducing the required power consumption.